Protecting device for electric detonators



Nov; 9, 1926. 1,606,418

H. L. GRANT PROTECTING DEVICE FOR ELECTRIC DETONATORS Filed NOV. 20, 1925 I Emmi Harry L. Grant, T

atented Nov. 9, 192 6.

uru'rno HARRY L'. GRANT, OF TAMAQUA, PENNSYLVANIA, ASSIGNOR TO ATLAS POWDER COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

IPROTECTING DEVICE F OR ELECTRIC DETONATORS.

Application filed November 20, 1925. Serial No. 70,369.

This invention relates to a protecting device for electric detonators of the character of that shown in my copending application, Serial No. 748,214, filed on November 6,

Like the device of the application referred to, the protecting device of the pres ent invention is intended to be applied to the lead-in wires of electric detonators and to serve, while in position, to establish a short circuit between the two lead-in wires, so that any stray currents imposed upon the lead-in wires, outwardly of the point of application of said device, may not find 1 their way to the detonator and prematurely explode the same.

I am aware of the fact that it has been proposedto short circuit the main firing cable leading from the blasting machine.

However, that method is of utility only atthe time of use. An important object of the present invention is to provide a structure which will be operative with respect to the individual detonators, at' all times between the time of manufacture of the detonator and until the same is actually exploded on the job, the structure being of particular utility during the time that the detonator is being transported "and while.it is being actual connection of its lead wires to the main firing cable.

The present application is directed to the protection of a specific form of short cir cuiting shunt and method of applying the same to the lead-in wires of the individual blasting caps, preferably with its inner end abutting and resting firmly against the terminal end of the usual insulation of the detonators. In the provision of a structure of this character, which is used only once and then thrown away, it is of importance that it be of a simple and inexpensive nature and one adapted to be applied rapidly by automatic machinery. With this end in view, I have devised the shunt shown in the accompanying drawing wherein.

Fig. 1 is a side elevation of a detonator having a spiral shunt applied thereto,

50 Fig. 2 .is a fragmentary side view of the same upon an enlarged scale,

' Fig. 3 is a cross sectional view of the shunt of Fig. 2 before its deformation by pressure,

Fig. 4 is a view of the shunt of Fig. 1

handled about the work preliminary to the shunt of Fig. 5.

Lure numerals designate corresponding parts in all of the figures of the drawing.

Referring to the drawing, 5 designates the conventional electric detonator and 6 and 7 designate the usual'lead-in wires of said detonator.

In the ordinary use of the detonator the flow of current of sufiicient strength past an ignitingclement 8, which connects the inner ends of the wires 6 and 7, explodes the detonator. The lead-in wires are insulated,

as indicated at 9 and 10, for some distance I from the detonator and the ends of the lead in wires are left bare beyond the point where the insulation terminates, to adapt them for ready application to the firingcable, leading from a blasting machine. v

The shunt of the present invention is formed from sections of spiral tubing which are cut to suitable lengths, the lead wires are threaded therethrough, and then the spiral tubing is deformed by pressure to press its convolutions into intimate contact with the lead wires at a plurality of points in the length of the latter. In the form of the invention illustrated in Figs. 1 to 4, 11 designates aspiral winding of wire of any suitable conductive material which may be a section of spiral tubing,

of circular form in cross section, preferably so positioned upon the lead wires 6 and 7 that its inner end abuts the insulation upon said lead wires. After the lead wires have been threaded through thesection ofspiral tubing, said tubing is deformed or flattened by the application of pressure to the form illustrated in Fig. 4, so that it tightly grips and engages the surfaces of said lead wires. The winding'll may be of copper, aluminum or any other suitable metal.

Inthe formof the invention illustrated in Figs. 5 and 6, the principle is the same, in thata tubular spiral is applied to the lead wires close enough to the insulation upon said lead wires to practically prevent the creation-of a' difference of potential between said wires, under any conditions. However,

in this case, the spiral winding, indicated at tudinally from said wires. This act of stripping the shunt from the Wires cleans and brightens them and puts them into condition to make effective electrical union with the main firing cable of the blasting machine.

It is to be noted that each and every convolution of the shunt will be pressed into contact with the lead wires, so that there will be a plurality of engaging surfaces, each of which will aid in the cleansing and scraping action as the shunt is stripped from the lead wires. It is not to be understood that the device is of utility only when actually touching the termination of the insulation. It will give-a very appreciable measure of protection even when spaced somewhat from the insulation because the influences which might bring about such difference in poten tial between the lead wires as to explode the detonator, are not those sought to be created by an intelligent human agency but only those which might accidentally occur.

Stray currents of such loW E. M. F. as to escape ordinary notice constitute a marked source of danger and are rendered absolutely harmless by this invention.

It is to be understood that the invention is not limited to any particular formation for the finished or compressed shunt but that it includes any spirally wound tubular shunt, the material of which is compressed into intimate and forcible contact with the surfaces of the lead wires after the lead wires have been threaded therethrough.

laving described my invention, what I claim is:

1. A shunt of the character described comprising a spiral of conductive ,material which has been flattened by pressure after application to thewires to be joined.

2. The combination with a detonator and its lead wires, portions of which lead Wires are covered with insulating material and the remainder of which lead wires are bare, of ashunt comprising a tubular spiral, positioned upon the bare portion of said wires and lying close enough to the terminal ends of the insulation to practically prevent the creation of a difference of potential between the lead wires inwardly of the point of application of the shunt, said spiral being deformed by pressure to cause its severalconvolutions to firmly engage the bared portions of the lead wires.

In testimony whereof he affixeshis signature.

HARRY L. GRANT. 

